I have an issue with binding multiple properties to a single
control. I have two lists called UserList and GroupList. I'm trying to display
a ListView of checkboxes of all the groups in the system. The UserList object
contains a list of integers based on the ID of the groups it is a member of. I'd
like to have the checkboxes be checked if the UserList object contains an ID of
a group in the groupList.

For example, the GroupList might contain IDs 1,2,3,4. While
the UserList has a list of IDs of 1 and 3. I'd therefore like checkboxes 1 and
3 checked, but 2 and 4 unchecked.

To do this, I need to bind to two different properties at
the same time and possible have some kind of converter. I'm pretty new to this
stuff, so I'm kind of stuck as to what to try next. Here's what I've currently
got -